Look on the glove box door for your serial number and give us that info, then we can figure out what you have.
OK, I've done some more research and it looks like you have a M60, not a C60. The M Series are the Tandems and the C Series are the single rear axle trucks. The M60 only came as a "trailing axle" tandem with the 292-I6 as it's standard engine and it had a GVW ranging from 24,000 to 30,000 pounds, so your 25,000 fits.
So, it looks like the Parts book calls for MC p/n 3896694 (shown on page 526). AND if I'm reading the parts book right the "KIt" for that MC calls it a 1-3/4 bore...p/n 3889707 (Wagner 46434).
Hope this helps,
Mike B
